As tests continue on three suspected cases of people contracting foot-and-mouth disease from animals, infection expert Professor Tony Hart from Liverpool University assesses the risks to human health.

How rare is it for humans to contract foot-and-mouth from animals?

The first point is that it looks as though it is highly infectious for animals. There are reports of it spreading by air for 150 miles or so.
With humans, it looks as though you need to have a massive virus dose before there is enough capable of causing an infection.

In the case of the slaughterman who may be infected, he got a great amount of gastric contents in his face and in his mouth so he had a very high dose of virus. It appears that very close contact is necessary for the infection to cross the species barrier from animals to man.

There are some reviews which report just over 40 cases worldwide. There has only been one well documented case in Britain and that is the one from 1967.

How do hand-foot-and-mouth and foot-and-mouth disease differ in animals?

Hand-foot-and-mouth disease is a common but mild infectious childhood disease. It is a febrile illness. Children will get a fever and perhaps go hot and cold. They will get a series of mouth blisters which will burst to become ulcers, then there will be blisters on their feet and hands.

Foot-and-mouth disease is the equivalent in animals. Cattle take the virus in, it grows in their intestine and goes through the bloodstream and re-emerges in the mouth to cause painful blisters and blistering on the hooves. The human disease is due to one human specific virus. The animal disease is due to another virus which is in the same family but only a distant relative and which rarely crosses to humans but is able to do.

All of the reported cases reported have been mild and self-limiting, meaning it gets better by itself.

If humans can catch it from animals, can it be passed from person to person?

We don't know that it cannot be passed from person to person. There has never been a case so far, so it looks as though it is quite difficult to catch from an animal in the first place and there has never been a case reported of it being passed from person to person.

Could a person who contracted the animal form pass it on to other animals and spread it further?

There have been some cases of humans acquiring the virus without getting diseased and then passing it on. It has happened that an infected human has re-transmitted it to another animal.

Should slaughtermen, or other people dealing with these animals, be vaccinated?

It is a good idea but medicine of any sort used for treating humans has got to go through rigorous testing and licensing. So although this has been licensed for use in certain animals, it has not been licensed for use on humans. It would be a big risk to vaccinate.

Are there sensible extra precautions that ought to be taken for people dealing with these animals?

If somebody suggested they should wear face masks, for example, that would not have prevented the case of this slaughterman because he got fluid directly in his face.There are precautions but it is almost like wearing space suits and slaughtermen would not be able to work in those. I repeat that it happens very rarely and when it does it is not a serious disease.

Should the public be alarmed about any prospect of an outbreak among humans?

From all the previous evidence I don't think that is likely. This disease is endemic in many tropical countries - in Africa and in South East Asia - there are very few reports from there. There are reports from Germany of people working with the virus in laboratories or factories and one factory has 50 years' experience of growing the virus. Handling the virus has produced only two cases of infection in that time.

So it looks as though it is difficult to become infected and once infection occurs, that person does not pass it on to somebody else. It is very specialised circumstances for transmission between the animal and human and since human-to-human transmission does not occur, it is very unlikely that there ever would be an outbreak.